1. Field of the Invention
The present invention relates to a method of controlling a vehicle active tilt control system. More particularly the present invention provides improved operating efficiency and operator/passenger comfort by selectively disabling the system under certain vehicle operating conditions.
2. Background Of The Invention
Automotive vehicles having suspensions are frequently equipped with stabilizer bars to reduce tilt or roll of the vehicle body relative to the suspension during vehicle maneuvers. The stabilizer bar is usually connected between the suspension arms of the vehicle wheels and frame or body structure. When the left and right wheels are in similar positions with respect to the frame or body, the stabilizer bar does not twist and therefore, it is effectively not there. When one wheel passes over a projection or depression in the road surface, or when the vehicle turns and the inside and outside wheels assume considerably different positions with respect to the frame or body, the stabilizer bar is twisted. This twisting motion induces a torsional resilient force for affecting the rolling characteristic of the vehicle and the road surface following characteristic of the vehicle wheels.
It is desirable that the torsional resilient force of the stabilizer bar can be adjusted in accordance with running or traveling conditions of the vehicle. Specifically, it is desirable to reduce the torsional rigidity during straight travel of the vehicle and to increase the torsional rigidity during turning of the vehicle. The reduced torsional rigidity enhances the road surface following characteristic of the vehicle wheels while the increased torsional rigidity enhances the roll characteristic of the vehicle.
Certain vehicle active tilt control systems include front and/or rear stabilizer bars which are adjustable by front and rear hydraulic actuators placed in lieu of the stabilizer bar linkages. The actuators are movable in extension and compression directions for adjusting vehicle body roll resistance provided by the stabilizer bars. A hydraulic pressure source must continuously supply pressurized fluid, controlled by electromechanical devices, to satisfy the hydraulic demand of the actuators. During straight line operation, the hydraulic system and the electromechanical valves consume valuable energy to be able to satisfy a command requiring pressurized hydraulic fluid. Additionally, static hydraulic fluid locked in the actuators provide a nominal value of resistance to suspension movement, which can be negatively perceived by vehicle operators and passengers, either as undesirable noise and ride harshness or ride motion.
It is therefore desirable to provide a method of controlling a vehicle active tilt control system which improves the operating efficiency and operator/passenger comfort through disabling the system under certain vehicle operating conditions.